Conventional methods to wrap or fasten a package require a user to use both hands. For example, to secure a package wrap with a tape, a user needs to hold the loose ends of the package wrap with one hand while taping them with another hand. Similar difficulty exists when using a Zipties® or Velcro® strap to secure a package. It requires a user to hold one end of the strap and the package in position with one hand while grasping the other end of the strap with the other hand in order to fasten the strap.
Within the field of material science, there has been an increasing study and development of shape memory polymers and shape memory alloys as a packaging material. Shape memory materials, such as shape memory polymers (SMP) and shape memory alloys (SMA) have the ability to return from a deformed state (temporary shape) to an original (e.g., baseline, memorized, permanent) shape induced by an external stimulus. For example, an SMP can exhibit change from a rigid state to an elastic state, then back to the rigid state using an external stimulus. The SMP in the elastic state can recover its “permanent” shape if left unrestrained. In similar respects, an SMA is an alloy that remembers its original shape and after undergoing deformation, is able to transform back to its pre-deformed, original shape when triggered to do so. As such, shape memory materials can be useful in various applications such as shrink wrapping, shrink tubing, and packaging.
Shrink wrap technology has been widely applied over or around a wide variety of items, such as roof tops, instruments, hazardous materials, cartoons, boxes, books, CDs, and DVDs. Shrink wrap technology relies on the use of a shape memory material (e.g., a polyolefin, polyethylene, polypropylene, PVC plastic film) which, when heated, shrinks and conforms to an object that it is covering. The shape memory material suitable for shrink wrap is available in a variety of thicknesses, clarities, strengths, and shrink ratios.
Shape memory materials have also been used to prepare expandable fasteners. U.S. Pat. No. 8,918,978 is directed to a method of joining a first component to a second component by aligning a first hole in the component with a second hole in the second component and inserting a fastener into the first hole and the second hole. The fastener comprises a shape memory alloy which is in a first shape having a diameter slightly larger than a diameter of the first hole and the second hole when the shape memory alloy is in an austenite state and reduced to a second shape having a diameter less than the diameter of the first hole and the second hole when the shape memory alloy is in a martensite state. After being inserted through the first and second holes, the fastener is heated to enable a phase transition to its austenite state, in which state the fastener has a diameter slightly larger than a diameter of the first hole and the second hole, and thus securely connects the two components.
A drawback in the prior art applications is that the shape memory materials give one or two different end shape results/permutations, with no gradual or intermediate shapes based on feedback. But sometimes, after initial setting of the shape memory material, an object enclosed by the shape memory material may slightly expand and/or contract as a result of shipment, transportation, or environmental factors (e.g. temperature, humidity). As such, the fasteners and packaging may cease to be fitted accurately on the underlying object and/or correspond in shape to the underlying object.
Therefore, it would be beneficial to provide a fastener or a closing device that provides self-assembling and/or self-closure about an object without manually maneuvering of the device relative to the object so that it is suitable for one handed or even hands free operation. Desirably, the fastener or the device may also conform to the shape of the object upon contact with an object to provide a tight and directed fitting. It would also be desirable for the fastener or the device to be able to automatically adjust the tightness and fitting of the package after the initial contact and also during a course of shipment or environmental changes.